Chemical Tests for Alkaloids in Pharmacognosy Laboratory
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Questions and Answers

What is the color obtained when Dragendorff’s Reagent is used to detect alkaloids?

  • Cream
  • Yellow
  • Purple
  • Reddish-brown (correct)

Which reagent is commonly used for the detection of caffeine based on its yellow color obtained?

  • Mayer’s Reagent
  • Picrolonic acid
  • Tannic acid
  • Hager’s Reagent (correct)

What color is typically obtained when mineral acids are used for the detection of alkaloids?

  • Bluish-violet to red
  • Yellow (correct)
  • Cream
  • Orange-red

What chemical composition is present in Marquis Reagent used for detecting amphetamines and opiates?

<p>Formaldehyde and conc.Sulfuric acid (A)</p> Signup and view all the answers

In the detection of colchicine, which chemical composition results in a bluish-violet to red color?

<p>p-Methylaminobenzaldehyde and sulfuric acid (C)</p> Signup and view all the answers

What color is obtained when Hager’s Reagent is used for the detection of alkaloids?

<p>Yellow (B)</p> Signup and view all the answers

Which reagent is used for the Murexide Test and results in a purple color?

<p>Potassium chlorate + HCl + NH3 (B)</p> Signup and view all the answers

Which reagent, when used, results in a reddish-brown color in the presence of alkaloids?

<p>Wagner’s Reagent (B)</p> Signup and view all the answers

What color is typically obtained when Tannic acid is used for the detection of alkaloids?

<p>Yellow (B)</p> Signup and view all the answers

Which chemical composition is present in Dragendorff’s Reagent?

<p>Potassium bismuth iodide solution (D)</p> Signup and view all the answers

In the detection of morphine, what chemical composition results in a deep purplish red color?

<p>Formaldehyde and conc. Sulfuric acid (C)</p> Signup and view all the answers

Flashcards

Dragendorff's Reagent Color

A reddish-brown color is obtained when Dragendorff’s Reagent is used to detect alkaloids.

Hager's Reagent for Caffeine

Hager's Reagent is commonly used for the detection of caffeine, producing a characteristic yellow color.

Mineral Acids and Alkaloids

Mineral acids react with alkaloids, typically resulting in a yellow color.

Marquis Reagent Composition

Marquis Reagent, composed of formaldehyde and concentrated sulfuric acid, is a reagent that produces color changes when reacting with amphetamines and opiates.

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Colchicine Detection Color

A bluish-violet to red color develops when using p-Methylaminobenzaldehyde and sulfuric acid to detect colchicine.

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Hager's Reagent Color

Hager's Reagent, like a yellow canary, signals the presence of alkaloids with its characteristic yellow color.

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Murexide Test Color

The Murexide Test, using potassium chlorate, hydrochloric acid, and ammonia, produces a purple color when alkaloids are present.

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Wagner's Reagent Color

Wagner's Reagent, similar to Dragendorff's, produces a reddish-brown color in the presence of alkaloids.

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Tannic Acid and Alkaloids

Tannic acid reacts with alkaloids, producing a yellow color, similar to what you might see with Hager's Reagent.

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Dragendorff's Reagent Components

Dragendorff's Reagent consists of a potassium bismuth iodide solution.

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Morphine Detection Color

Formaldehyde and concentrated sulfuric acid, similar to Marquis Reagent, are used in a test that creates a deep purplish-red color for morphine detection.

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Study Notes

Reagents Used in Detection of Alkaloids

  • Mayer's Reagent: potassium mercuric iodide solution, produces a cream-colored reaction
  • Wagner's Reagent: solution of iodine in potassium iodide, produces a reddish-brown reaction
  • Dragendorff's Reagent: potassium bismuth iodide solution, produces a reddish-brown reaction
  • Hager's Reagent: saturated solution of picric acid, produces a yellow reaction
  • Picrolonic acid: picrolonic acid solution, produces a yellow reaction
  • Tannic acid: produces a yellow crystalline precipitate

Reagents Used in Detection of Specific Alkaloids

  • Murexide Test: potassium chlorate, HCl, and NH3, produces a purple reaction (caffeine)
  • Mineral acids: phosphotungstic acid and phosphomolybdic acid, produce a yellow reaction
  • Acidic p-methyl aminobenzaldehyde: p-methylaminobenzaldehyde and sulfuric acid, produces a bluish-violet to red reaction (colchicine)
  • Nitric acid: dilute nitric acid, produces an orange-red reaction (indole)
  • Marquis Reagent: formaldehyde and concentrated sulfuric acid, produces:
    • Purple to black reaction (ecstasy)
    • Orange to brown reaction (amphetamine)
    • Deep purplish-red reaction (morphine)

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Description

This quiz covers various reagents used in the detection of alkaloids, their chemical composition, and the color obtained as a result. Examples include Mayer's Reagent, Wagner's Reagent, Dragendorff's Reagent, Hager's Reagent, and Picrolonic acid.

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